Method of making a rubber lined impeller



June 1965 c. L. BABB 3,189,671

METHOD OF MAKING A RUBBER LINED IMPELLER Original Filed April 14; 1959 2 Sheets-Sheet 1 June 15, 1965 c. BABB 3,189,671

- METHOD OF MAKING A RUBBER LINED IMPELLER Original Filed April 14, 1959 2 Sheets-Sheet 2 United States Patent "Ofi ice 3,189,671 Patented June 15, 1965 3,189,671 METHOD OF MAKING A RUBBER LINED IMPELLER Charles L. Babb, Brookfield, Wis., assignor to Allisgl almers Manufacturing Company, Milwaukee,

is. Continuation of appiication Ser. No. 806,351, Apr. 14, 1959. This application Feb. 12, 1962, Ser. No. 174,654 4 Claims. (Cl. 264-247) This invention relates to centrifugal pumps and more particularly to rubber lined impellers for centrifugal pumps and is a continuation of application S.N. 806,351, filed April 14, 1959, by Charles L. Babb, entitled Rubber Lined Impeller and Method of Making Same and now abandoned.

In a variety of industries there is a demand for a centrifugal pump capable of resisting the abrasive action of liquid suspended coarse materials. With pumps having standard metal surfaced impellers the abrasive material gradually scores and pits the impellers surface. This eventually requires a work stoppage and replacement of the impeller. To solve this problem the past has seen the use of an impeller lining of rubber or similar resilient material capable of handling various abrasive solids. With open type impellers it is relatively simple to mold a rubber covering having the various curvatures needed to provide an efiicient pump. However, with closed type impellers of the past there have been undesirable sharp molded edges which reduce the etficiency of the pump.

7 In particular, rubber lined closed impellers of the past have been molded with a sharp right angle corner about the inner periphery of the impellers intake. This sharp corner is in effect a projection which prevents the incoming liquid from following a smoothly curved flow course into the impeller vanes. The consequence is flow turbulence causing a drop in the pumps efliciency.

The impeller of this invention has a unitary rubber molded coating with a convex surface for the periphery of the intake whereby an increase in efiiciency is obtained. Inasmuch as the power now required to drive the pump at a specific rating is less, the size of the driving motor may be reduced.

It is, therefore, one object of this invention to manufacture for use in a centrifugal pump a new and improved closed type impeller having a bonded unitary rubber coating.

Another object of this invention is to manufacture for use in a centrifugal pump a new and improved rubber lined closed type impeller having a more efficient intake.

A further object of this invention is a method of forming a rubber lined closed type impeller having free flowing surfaces.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawing in which:

FIG. 1 is a perspective view of a rubber covered closed type impeller formed in accordance with this invention;

FIG. 2 is a cross sectional view of the impeller and a cylindrical mold used to form the impeller;

FIG. 3 is a partial perspective view of the mold with a mold element detached to show its special configuration; and

FIG. 4 is a perspective view of a cover for the mold of FIG. 3.

In accordance with this invention and as illustrated in FIG. 1 a rubber lined closed type impeller 11 is provided in which a rubber covering 12 cooperates to provide a final form of unitary construction, that is, a one piece article. The impeller comprises an annular ring 16 and a disk 17 (see FIG. 2) in axial relation for concentric mounting about a pump shaft, not shown. Mounted between the ring 16 and disk 17 are a plurality of radially extending arcuate metal vanes 18, one of which is shown. Disk 17 is provided with an internally threaded hub member 21 for receiving the pump shaft. When assembled the ring and disk and vanes 18 form the impellers skeleton 19 which reinforces the rubber cover 12.

Ring 16 defines an inlet or suction opening 22 through which incoming fluid flows. Inlet 22 is in hydraulic communication with passages 23 formed by the vanes 18 and ring and disk. To strive toward a pump of high efficiency the flow path through the inlet 22 and into the passages 23 should have a smooth contour providing turbulence free flow. The pump of this invention has achieved this goal by providing about the inner periphery of inlet 22 a molded rubber convex surface 26 (FIG. 2) which is unilary with the other surfaces of the molded impeller.

In manufacturing a rubber lined closed type impeller having a convex surface 26 in the inner portion of the inlet 22 split blade forming cores 27 are used. These split blade cores are used to form the layers of rubber 12 or other similar material about the impeller skeleton 19 and must be designed in such a manner as to permit removal of the blade cores without damaging the molded impeller. Thus, as illustrated in FIG. 2 and more clearly. in FIG. 3, each blade core comprises two sections 28 and 29. The first core section 28 has two flat lateral surfaces 32 and 33, and the second section 29 has one flat lateral surface 36 with the other lateral surface having a concave surface 37. It is this concave surface in the second section that provides the convex surface 26 in the inlet of .the impeller.

In molding the impeller an annular extractor plate 38 is placed in the base of an appropriate molding tank 39. Disk 17 with vanes 18 secured thereto, such as by welds, is then placed on the extractor plate. Base 42 of impeller hub 21 is of a predetermined height in order to properly space the disk 17 to form the rubber molded covering about the disk. A threaded positioning plug 43 is inserted through the tank 39 and into the impeller hub 42 to center the impeller and prevent rubber from entering the hub. The first series of split core sections 28 are then placed over an extending ridge 44 of the extraction plate 38. As illustrated in FIGS, 2 and 3 these first sections extend radially outward and are spaced parallel to the impeller skeleton in order to give a proper thickness of rubber coating on the skeleton. The second series of core sections 29 which have the curved portion 37 are then placed .over the first sections. Ring 16 is then located on the vanes 18 with the assistance of locating pins 45. The blade cores may be secured in their spaced relation by pins not shown.

During assembly of the mold and impeller skeleton, unvulcanized rubber compound is introduced so that insubsequent curing operations the impeller skeleton is covered by rubber to a predetermined thickness. After introduction of the rubber a cover 46 as shown in FIGS. 2 and 4, with an inwardly extending inlet forming core 47 is secured to the tank. An inner protruding portion 48 of the cover cooperates with ring 16 in a spaced relationship to form the impellers front shroud 51. Then the entire mold assembly is placed under high temperature and pressure for curing.

After the rubber 12 on the impeller skeleton 19 has become cured the tank cover 46 is taken off to remove the rubber lined impeller from the tank 39. Ejector pins 52 which extend through the bottom of the tank and are in contact with the extraction plate 38 and plug 43 are then pushed upwardly. In such a manner the extraction plate which supports the now rubber lined impeller and the blade cores is pushed upwardly and out of the tank.

I; removed between the back plate 49'and front shroud 1 t-ioned 'dilficulty. I blade is laterally removed'past the outer periphery of the ring and disk, This is permissible because this section has only fiat lateral surfaces 32 and 33. "After the lower core 7 "sections have been removed the upper blade core sections 29Iare moved down to the position originally assumed by to be performed, I declare that what I claim is:

The blade cores are now ready'to be extracted from the impeller; V f

7 It should first unit blade cores cannot be extracted from a closed rn be appreciated that conventionalfsingle pellerif the cores havea curved surface 37 such as shown in :thedual unit cores 28 and 2 9 of this invention, Thl'S is because blade cores for a'closed impeller are laterally l in aj-path coincident to centrifugal lines of action; If

such a core is a single unit and has, in addition to its lateral curvature, a curved surface 37 extending upwardlyinto the inlet of the impellerthen the molded surface 26 of'the impellers inlet would preventlateral'with drawal of the core. The use of the split coresections 28 and 29 in this invention has overcome the aforemen- The lower core sectionJZtS of each the lower core s'ections ZS In such a position the upper disk; securingqsaidring to said vanes in spaced snbstan tially parallel'relation to said disk; introducing an amount. of rubber iIltOiSflid tank mold to form an integral coats v ing a'bou-tsaid skeleton; curing said rubbergla-terally with drawing-the core sections adjacent said disk from between core sections 29 are now cleariofi the inner convex surface 2630f the inlet and can-be laterally removed.

The resulting product is a rubber lined cl'osed type impellerfwith a flow surface having smooth gradually Although only one embodiment skilled in the art' that various changes and modifications Y may be made therein Without departing from the spirit of the invention or the scope of the appended claims.

Having now particularly described and ascertained the natureof my said invention and the manner in which itis 1; In the method of iorming a rubber molded closed 1 a type irnpeller having a keletoncomprising an annular ring and a disk spaced therefrom by plurality of vane V of this inventionhas been illustrated and described it will be apparent to those curved contour lines. In obtaining this result whilernolding the impeller in a unitary construction a more efiicient ,and durable impeller is prov-ided.

members the steps of: positioning said skeleton in a tank mold with a blade core betweeneach vane member in spaced relation therefrom and from said ring andsaid disk; each blade core being composed of; two sections in, contact along'aplane 'substantially parallel to the plane of'said disk; introducing an amount of'rub-ber into said tank mold i to form an integral coating about said skeleton; curing said "rubber; laterally withdrawing the .core sections. adjacent said disk from between said vane members; moving the remainin'g core sections to the 'positions originally -a'ssumed by the removed core sections .forfl-ike, lateral Withdrawal and laterally withdrawing said remaining core' sections from between said vane members. a

2. In the method of forming a rubber molded closed type .impeller having a skeleton: comprising an impeller ring and a disk spaced therefrom by aplurality of vane membersaand including an inlet defined by said annular V ring the steps of: positioning said skeleton in a tank mold' f with .a bladeco're positioned betweeneach of said vane 'rnember' s; positioning an inlet core in said inlet in said annularring, one of said cores being sectionalized to per- V individual sectional removal thereof; introducing an amountof rubber into said-tank mold to form an integral 9 coating about said'skeleton; curing said rubber; remo ing; the other of said sections of said one of said cores; mov'=" ring "said one of :saidsectionstothe Positionoriginally ocf pied by said other of said cores for like removal there f;

' and removing the other of said'cores.

V 3. In the method of torming an integrally rubber mold? 1 ed closed type impellerl aving a metal skeleton'comprising an annular ring and a vdisk having a plurality of cir curnferentially spaced vane' members secured thereto the 5 steps ofzt positioning said. disk with said vanes in a tank mold; positioning a blade coreibetween each vane mernher in spaced relation therefrom and from said disk; each blade .core being composed of two sections in" contact alonga plane substantially parallel to the p-lane'oif said said ,vane members; moving said remaining core sec? ,tions to the positions originally assumed by said removed core sections for likelateral withdrawal; and laterally :Withdrawing said remaining core sections from between said vane members. i 7 7 w t 4-. In the method of formingan integrally ,rubber'rnolded closed type impeller having a metal skeleton'eornpris 1 ing an annular ring having the .inner'annular lip thereof curled upwardand a'dis'k spaced therefrorn'bya plurality of vane members the stepsof: positioningfsaid' skeleton in a :tank mold with a plurality or bladecoresbetween each vane member in spaced relation'therefrom and-from said ring and disk, each blade core, being com posed of two sections in removable contact along a plane I, 7' parallel to the plane of saidsdisk; each oore'section re- J mote from'said disk havinga concave surface adjacent said curved lip; introducing-an amount of rubben'into integral coating aboutsaid skeleton; curing-said rubber; l aterally withdrawing the said tankmold to form an core sections adjacent said disk from between said vane members; moving the remaining core sectionsto the po-g sitions originally assumcdby thefrem-oved core: sections for like lateral withdrawal; and laterally withdrawingsaid remaining core sections from between said vane members 7 References Cited by the Examiner UNI E srArEs' PATENTS v V V 1037;VXR V V ALEXANDER BRODMERKEL, Primary [Er-miner. WILLIAM J. STEPHEN O 'Exami Ler. 

1. IN THE METHOD OF FORMING A RUBBER MOLDED CLOSED TYPE IMPELLER HAVING A SKELETON COMPRISING AN ANNULAR RING AND A DISK SPACED THEREFROM BY PLURALITY OF VANE MEMBERS THE STEPS OF: POSITIONING SAID SKELETON IN A TANK MOLD WITH A BLADE CORE BETWEEN EACH VANE MEMBER IN SPACED RELATION THEREFROM AND FROM SAID RING AND SAID DISK, EACH BLADE CORE BEING COMPOSED OF TWO SECTIONS IN CONTACT ALONG A PLANE SUBSTANTIALLY PARALLEL TO THE PLANE TO SAID DISK; INTRODUCING AN AMOUNT OF RUBBER INTO SAID TANK MOLD TO FORM AN INTEGRAL COATING ABOUT SAID SKELETON; CURING SAID RUBBER; LATERALLY WITHDRAWING THE CORE SECTIONS ADJACENT SAID DISK FROM BETWEEN SAID VANE MEMBERS; MOVING THE REMAINING CORE SECTIONS TO THE POSITIONS ORIGINALLY ASSUMED BY THE REMOVED CORE SECTIONS FOR LIKE LATERAL WITHDRAWAL AND LATERALLY WITHDRAWING SAID REMAINING CORE SECTIONS FROM BETWEEN SAID VANE MEMBERS. 